I want to switch from Mac Thunderbird to Mac Mail. To do so, I compressed all folders of the account in Thunderbird and after that, I used the import wizard of Mac Mail. Unfortunately, a lot of Mails are missing. A folder that contains hundreds of mails in Thunderbird, contains only one message in Mail, but I get no errors or warnings. How can I migrate my local folder? (I cannot switch to IMAP, thank you ;-) )
A friend of mine had a similar problem when migrating local mails from a POP mail account from Windows XP (Thunderbird) to a Mac (Mail.app).
This is what we did:
(You may consider keeping the IMAP mail address...)
This may be easier than troubleshooting why the import doesn't work properly.